Apparatus for controlling combustion mechanisms



ew. 26, 1935. F. s. DENISON 2,022,188

APPARATUS FOR CONTROLLING COMBUSTION MECHANISMS I Original Filed June2'7, B25 3 Sheets-Sheet 1 [ml/6122502" FEEDER/(K JI DEN/JON F. S.DENiSON APPARATUS FOR CONTROLLING COMBUSTION MECHANISMS No'v. 26, 1935.

3 Sheets-Sheet 3 Original Fi led June 2'7,

POWER Luv: suPPLy CURGUIT MOTOR CIRCUIT Room THER MosTAT COMBUSTIONSPARK [ml/ado? EQwER/CKJDEN/Jo/V 9&4 2 2w? M e ATToEN'EYs Patented Nov.26', 1935 UNITED STATES PATENT OFFICE APPARATUS FOR CONTROLLING COMBUS-TION MECHANISMS Delaware Original application June 27, 1925, Serial No.

Divided and this application June 25,

1928, Serial No. 288,201

47 Claims. (Cl. 158-28) This invention relates to new and usefulimprovements in the methods of and apparatus for controlling combustionmechanisms and more particularly relates to such mechanisms having afuel feeding apparatus which is electrically controlled.

This application is divisional of my copending application for circuitmaker and breaker, filed June 27, 1925, Serial Number 40,086 now PatentNo. 1,732,182 issued October 15, 1929 and Reissue Patent No. 17,993issued March 10, 1931.

It is common especially in the art of oil-burners to employthermostatically controlled bumers which control not only effects thestarting and stopping of the burner operation and fuel feeding but alsoignition therefor. It is highly advantageous to employ a safety meanswhich will automatically stop the fuel feeding upon failure ofcombustion of the fed fuel whether such :0 failure of combustion occursinitially or intermediately during the fuel feeding. In this novelinvention, a safety means is provided which is automatically operableupon starting of the fuelfeeding to stop the same after a predeterminedinterval. This novel process and apparatus also includes the use of thecombustion of the fuel as a control medium to render the safety meansinoperative before completion of its stopping function and, further,this control medium may 30 also be used to stop operation of an ignitionmeans.

Further, this process provides the controlling of an electricallyoperated fuel feeding apparatus which consists in closing a circuit tothe fuel feeding means to operate the same, providing an ignition meansfor the feed fuel, causing the safety means upon closure of the circuitto start functioning automatically to stop the fuel feeding after apredetermined interval, using the heat of combustion ofthe fuel as acontrol medium to render the safety means inoperative before completionof its function, and using the failure of combustion while said circuitis closed as a control medium to permit said safety means to functiontostop the fuel feeding after a predetermined interval.

The object therefore of this invention is to provide a method of, andapparatus for, controlling combustion mechanisms.

Another object of this invention is the provision of an improved form ofcircuit controlling spparatus.

Other objects of-the invention will more fully appear from the followingdescription and the accompanying drawings and will be pointed out in theannexed claims.

In the drawings there has been disclosed a structure designed to carryout the various objects of the invention, but it is to be understood 5that the invention is not confined to the exact features shown asvarious changes may-be made within the scope of the claims which follow.

In the drawings:

Figure l is a view in side elevation of a thermo- 10 static membermounted so that its thermostatic element is responsive to the heat ofcombustion, the mounting being shown in section;

Figure 2 is a cross-sectional view on the line 2-2 of Figure 1;

Figure 3 is a similar view on the line 3-3 of Figure 1;

Figure 4 is a view of the disc and movable parts in the intermediatepositions assumed when the two of the contacts are disengaged and twoare still engaged Figure 5 is a view similar to the foregoing butshowing all contacts disengaged.

Figure 6 is a wiring diagram of the apparatus embodying the invention;and

Figure 7 is another wiring diagram showing a modified construction.

This novel process and apparatus may be explained and illustrated. inconjunction with relay control mechanism. The construction and operationof such mechanism will be first described and then the automatic cut-outor safety switch and thereafter the device which is adapted to renderinoperative the safety switch when the device is affected by the heat ofcombustion.

The fuel feeding device may include an electric motor 1 which is adaptedto operate a blower to jet the fuel, such as oil, to the burner head, orto operate a centrifugal burner head with or without an oil pump. Theseparts are old and well known in this art and need not be furtherillustrated or described. The motor 1 may receive electrical energy fromthe power lines 8' and 9 through a motor switch which is automaticallycontrolled as, for example, by a thermostat in the room or other placeto be heated.

In the form here disclosed the thermostat comprises a substantiallyring-like bar H which has securely attached thereto a relatively stiffmetallic member such as the blade l2 formed of a bar of suitable metalwhich is an electric conductor. As the mechanism is preferably mountedin an upright position, the blade l2 depends from the thermo-bar II.This ring-like bar is mounted, as is usual upon insulating material. I

' connected to the wire I5 and the contact I4 is so connected to thewire I6. I

A single control circuit is preferably used and it may be closed acrossthe contacts I3-I4 and. in the form shown, the circuit-closing meansconsists of a pair of members adapted to be successively engaged withtheir respective contacts. The relatively stiff blade I2 is carried bythe thermobar II and-is adapted to engage the contact I3 in order toform an electrical connection therewith. A flexible blade I! is alsocarried by the thermo-bar II as by being welded to the blade I2. Theblades I2 and I! are so arranged that they terminally diverge and eachbears a contact tip I8. The contact tip of the flexible blade I1 isadapted to engage the end of the lower contact I4. This flexible blade II is also provided with an aperture I9 so that the other contact I3 mayfreely be passed therethrough, the resultant air gap providingsuflicient insulation between the tion between the backing plate 2| andblade I2.

It may also be noted that the backing plate 2I is 7 provided with anaperture similar to the aperture IS in flexible blade I! and for thesame purpose. In addition to the thermostatic circuit wires I5 and I6,which are respectively connected to the contacts I3 and I4, asupplemental wire 22 is electrically connected to the thermo-bar I Iand, hence to the blades I2 and I1.

'I'he'switch forming a portion of the relay control mechanism may nextbe described in conjunction with its connections. The switch ispreferably borne by a panel usually mounted in a vertical position. Anelectro-magnetic coil 23 is mounted thereon to attract, when energized,an armature 24 having a weighted portion 25 and mounted upon a pivot pin26. This armature lever has an arm 21 projecting beyond the pin 26 toengage and normally uphold a counterweight 28 connected to the parallelswitch arms 29 each'bearing a contact tip 3| for electrical engagementwith the relatively fixed terminals 35 of the main lead wires 32 and 33from the power lines 8 and 8. These switch arms are pivotally mountedupon the pivot posts 34 and the counterweight 28 normally tends toretain each tip 3| in contact with the respective terminal contacts 35of the lead wires 32 and 33, the opening movement being limited by theadjustable screw 36. Upon close of these switch arms 29, electricalenergy passes from the line 8 to the lead wire 33 to contact 35 toswitch-arm contact 3 I, through the switch arm to post 34 and, by wire31 to the device to be energized such as the burner motor I3 of the roomthermostat.

the force of the counterweight 28 and normally holds the switch-arms inopen position. However, upon energization of the electro-magnet 23,

the'force of the weight 25 is removed, and the counter-weight may closethe switch-arms where 5 they remain until the electromagnet isde-energized whereby the weight 25 may indirectly open .the switch-arms.

The energization and de-energization of the electromagnet is effected bymeans of the thermo- 10 static mechanism above mentioned. The twoswitch-arms 29 are conventionally represented as tied together by thebar 39 because they function as a unit in pivotal movements upon theirposts 34. The electromagnet 23 is in series with the 15 wire 4| which isterminally connected to the low voltage secondary side of a step downtransformer 42 which has its primary constantly energized by its shuntcircuits 43-44 from the lines 32--33. The. wire I6 leads from the otherend of the sec- 20 ondary of this transformer to the thermostat contactI4. g

In the wiring diagram, the parts are represented in the positionsoccupied when the blower motor] is shut ofi and the thermostat, usually25 positioned in the room or place to be heated, is

warm enough to hold the blades from circuit-closing position so that theelectromagnet circuit is open at the posts I3 and I4. As the thermo-barcools, the blades I2 and I1 and the backing plate 30 2| move toward thecontacts I3 and I4. Owing to the divergent relation of these two blades,the relatively flexible blade I1 first engages the lower contact I4. Insuch position, the upper contact I3 is freely passed through the alinedapertures 35 in the plate 2I and blade I I and is out of electricalconnection therewith while the other blade I2 is spaced from its contactI3. The electromagnet circuit thus remains open, being broken at theposts. Further movement of the cooling 4U thermo-bar causes engagementof the still blade I2 with its contact I3. The backing plate maintainsits spaced relation from the blade I2 while the blade II flexiblyremains in contact with its contact I4. Thus, the contacts aresuccessively made and the electromagnet circuit is closed across thecontact screws so that the electromagnet is energized, its armatureweight 25 is raised which permits the weight 28 to drop and thus to movethe switch arms 29 into position closing b the main line circuit to themotor. One of the switch arms 29 carries a short arm 45 which iselectrically connected to the wire 4I leading from the electromagnetto-the contact I3 through the combustion-affected thermo-switch as willbe later described. However, this arm 45 is adapted, when theswitch-arms are closed, to effect electrical engagement with therelatively fixed contact 46 which is connected by the wire 22 to theroom thermo-bar II. Thus, when the switcharms 29 are moved tocircuit-closing position, the arm 45 by contact at 46 shunts the portionof the wire 4| connecting the post 34 and its normalcircuit-continuation via the wire I5 to the post This condition obc5tains so long as the electro-magnet 23 remains energized and anyaccidental break in the current from the power line will de-energize theelectromagnet and cause the motor circuit to be opened by force ofgravity acting through the weight 2'5 70 which is heavier than thecounterweight 28 and"- is therefore able to open the switch-arms 29against the pull of the counterweight 28.

However, disregarding such abnormal or accidental condition, themot'or-switch-arms may be caused to be opened by movement of thethermobar II when it becomes heated and successively moves the blades l2and H from their contacts. The circuit is not interrupted until thethermobar has moved a predetermined distance. Such a lag in the breakingis provided by the use of the relatively stiff and flexible contactbiades and the supplemental connection for the thermo-bar and blades.Thus, as the heating thermo-bar moves, the stiff blade I2 is firstdisengaged from its post I3 and in such position, the contact I3 and itsconnections via wire l5 and wirev 4| up to the supplementary switch arm45 are de-energized but, the circuit from the electro-magnet ismaintained across the arm 45, fixed contact 46 and wire 22 to thethermo-bar II, and flexible blade l1, contact l4, wire l6, transformer42,- and Wire 4| to the electromagnet 23. The leads from the supply orpower lines are thus maintained closed and supply electrical energy tothe motor 1. When the thermo-bar has continued its opening movement forthe predetermined distance or v lag, the flexible blade H is moved fromits contact l4 and the circuit is opened. The relatively stiff metallicbacking plate 2 I. being movable with the blade l2 assures the openingtravel of the flexible blade I1 in timed relation to that of the stiffblade I2. When the electromagnet circuit is thus opened, the armatureweight 25 drops and, through the lever 21, rocks the lightercounterweight 28 of the switch-arms, moving the latter as well as theshort arm 45 to open positions for a subsequent cycle of operations.

The novel safety means featured in this invention and hereinbeforementioned consists'of an automatically operable circuit-breakerinterposed in the relay circuit and also a. thermostatically controlleddevice adapted to be mounted so as to be responsive to conditions ofcombustion automatically to affect the operation of the circuitbreakerto interrupt the fuel feeding means or burner motor in case of ignitionfailure upon initial starting of the fuel feeding means.

The thermostatically controlled device will next be described and, asshown in Figures 1, 2 and 3, comprises the casing 45 which preferably isopen on one side as shown in Figures 2 and 3. A closure 46 is providedto close the open side of the casing as shown to prevent dust andforeign material from getting thereinto and affecting the operatingmechanism mounted therein. A flanged bracket 41 is secured to the casing45'to provide a means for securing it to a supporting means such, forexample, as the stack 48 of the furnace or heating plant. Athermo-element 49 has one end secured to the bracket 41 and inwardlyprojects into the stack 48 so as to be di rectly affected by theproducts of combustion when ignition takes place. A cap 5! is secured tothe end of the thermo-element 49 and has a stem 52 secured thereto whichextends through the thermo-element and into the casing 45 asparticularly shown in Figure l. The coefficient of expansion of thethermo-element 49 is cbvicwthe pin 58 passes, is preferably elongated soas to permit the stem to relatively move with reference to the arm 51when the contacts of the device are in circuit closing position as shownin Figure 1. A tension spring 6| has one end terminally secured to thearm 51 and its other end to the easing wall, thereby constantly exertinga pull on the arm which tends to move the switch arm 53, and thereforethe contact 54, into circuit closing position.

A disc 62 is also mounted upon the stud 55 and is frictionally preventedfrom relative rotation thereon by means of a tension member 63interposed between the lower face of the hub of the switch arm 53 andthe upper face of the hub 56 in the absence of a positive drive. (SeeFigure 2.) A flexible contact member 64, having a contact tip 65 on eachside thereof, is mounted in a stud 66, secured to the disc 62 insulatedtherefrom, as shown in Figure l. A wire 61 electrically connects thestud 66 and therefore the contact member 64 with a terminal post 68mounted in the wall of the casing in insulated relation thereto. Whenthe thermo-element 49 is cold, as when before combustion takes place,the contact screw 54 will be moved into contact with one of the contacttips 65 of the member 64, thereby electrically connecting the terminalpost 68 with a similar terminal post 69 mounted in the Wall of theeasing and not insulated therefrom so that current may pass from thepost 68 through the wire 61, flexible member 64, contact tip 65, screw54, switch arm 53, stud 55 and through the casing wall to the post 69. Athird terminal post 1| is also mounted in the casing wall in insulatedrelation thereto and is electrically connected to a post 12, mountedupon the disc 62 but insulated therefrom, by means of a flexibleconnection 13. A contact screw 14 is adjustably mounted on the post 12and is adapted to be engaged by the fiexible contact member 64 to closea circuit between the terminal posts 68 and 1|.

An important feature of this invention resides in the construction ofthe novel switch mechanism' above described, and in the order in whichthe switch contacts 54, 65 and 14 are moved into and out ofcircuit-closing and circuit-opening positions by the action of thetherrno-element 49 which, as before stated, is directly responsive toconditions of combustion in the burner. These switch contacts are soarranged that the time interval required to move them intocircuit-opening and circuit-closing positions may be varied to anydesired degree. They are also arranged to successively open and closeduring each cycle of operation.

The means provided for controlling the timed relation between theopening and closing of the contacts preferably consists in mounting uponthe disc 62 a pair of posts and having stop screws 16 and 11,respectively, adjusuably mounted therein. The stop screw 16 is adaptedto be terminally engaged by the switch arm 53 when moved into theposition shown in Figure 5. The

stop screw 11 has a. headed pin 18 secured thereto which extends throughan aperture in the flexible member 64 so that when the contact screw 54is "moved out of contact with the tip of the tip 65 of the member 84 asshown. Obviously the post 15 is insulated from the disc 62 in order toprevent the current from short circuiting between the posts 15 and 12.By adjusting the stop screws '16 and II, the air gap between the contactscrew 54 and its complementary contact tip 65 and also between thecontact screw 14 and the other tip 65 on the opposite side of theflexible member 64, may be increased or decreased to obtain the desiredtime interval in the opening and closing of the contacts.

The disc carries on its lower face a pin H! which cooperates with a stoplug 83 secured to a wall of the casing for a purpose to be more fullypointed out hereinafter, and for cooperation with a lever 8| which ispivoted to the casing at 82 and extends outside thereof through a slotas clearly shown in Figs. 2 and 3. It will be noted from these figuresthat the lever is so formed as to clear the stop lug 83. Its functionwill become more apparent as the description proceeds.

When the basement or other space in which the combustion switch islocated is at normal ambient temperature and the furnace is at the sametemperature the parts assume the relative positions shown inFig. 1wherein the pin 58 is in the middle of the slot 59 of the stem 52, pin19 is abutting against stop lug 83-under the influence of spring 6|, andthe various contacts are closed. If the burner of the furnace is nowstarted, the temperature of the thermostat will rise and stem 52 willconsequently move upwardly (looking at Fig. 1).

When the temperature of the thermostat gets slightly beyond 'that whichnormally obtains in the basement the pin 58 will be engaged by the lowerend of the slot 59 and upon further heating of the thermostat the bellcrank switch arm |-53 will be rotated in clockwise direction. In thecourse of such rotation the disc 62 and accordingly contact 14, willfirst be held stationary due to its frictional mounting, previouslyexplained, with the resultant that thespace between contacts 54 and 14will be increased. Due to the flexible nature of the arm 64, contact 65will follow contact 54' thus separating itself from contact 14. Tip 18will also remain stationary with the result that upon further heating ofthe thermostat and further rotation of switch arm 53, arm 64 will engagetip 18 as shown in Fig. 4 to prevent further following movement ofcontact 65 so that this contact will be separated from contact 54.Further rotation of switch arm 53 causes it to engage adjustable stop 16as shown in Fig. 5. When this occurs there is a direct drivingconnection between the stem 52 and the disc 62 whereby upon furtherheating of the thermostat the disc is rotated in spite of its frictionalmounting, carrying with it the contacts in the relative positions shownin Fig. 5.

As soon as combustion within the' furnace ceases the thermostat willbegin to cool, stem 52 'willbegin to'move in the opposite direction, and

the thremostat was the hottest because of its frictional mounting.Therefore when arm 53 begins the aforementioned counter-clockwiserotation the gap between contacts 54 and 65 will be closed and thesecontacts will be .brought into engagement. Continued rotation will pushcontact 65 into engagement with contact I4. When this occurs all threecontacts are in engagement the operation of the contacts.

with each other and arm 53 has a direct driving connection with disc 62through the contacts and post 12. Continued cooling of the thermostattherefore causes rotation of disc 62 in counterclockwise direction. Whenthe thermostat 5 reaches a temperature slightly above the normal ambientbasement temperature, pin 19 will engage stop 83 thereby preventingfurther rotation of the disc by means of spring 6|. Fur ther movement ofstem 52 due to further cool- 10 ing of the thermostat to basementtemperature is taken up in the slot 59. All ambient temperature changesoccurring while the furnace is out of operation are similarly taken-upin the slot 59 without affecting the contacts by reason of engagement ofpin 19 with stop 83 under the tension of spring 6 I.

' Thus in normal operation the thermostat will upon being heated up fromcold position operate to first disengage contacts 85 and 14 while leav-20 ing contacts 54 and 65 in engagement, and then separate these lattercontacts whereby all of them are electrically disconnected. Uponcooling, contacts 54 and 65 are first brought into engagement and theseare subsequently moved into engagement with contact 14. As previouslystated, the purpose of providing adjustable screws 14, 16 and I1 is toenable adjustment of the timing of This will, now be more clearlyapparent from the foregoing description of operation.

The purpose of lever 8| is to enable a manual closure of the combustionswitch contacts while the stack is hot for purposes of test orinspection In the absence of this lever, it would be necessary for theinspector to open the casing and manipulate disc 62, or wait for thestack to tool. In normal operation the lever 8| performs no function. I

Referring to Figure 6, it will be noted that the 40 wire l5 leading fromthe contact l3 of the room thermostat is connected to the terminal post69 of the above described switch mechanism which will hereinafter bereferred to as the combustion thermostat. A wire 84 also leads from theterminal 69 to one side of an ignition circuit comprising the wires 85and 86, the latter being connected by a wire 81 to the low voltagesecondary of a transformer 88 as shown. The other side of the step downtransformer secondary is connected to the terminal 68 by means of a wire89. The form of ignition means shown in Figure 6 pref erably comprises agas valve 9| which is automatically operable by means of a relay coil 92connected in series with the wires 85 and 86 and therefore the secondaryside of the transformer 88. A spark coil 93, of ordinary construction,also has one of its windings connected in series with the transformer 88through the combustion thermostat while the high tension winding thereofis connected in series with a spark plug 94 as shown. The abovedescribed method. of ignition is commonly known as a combination gas andspark and is well known in the art; The wire 4| leading from the post 34of the motor switch is connected to the third terminal post II of thecombustion thermostat. It will also be noted that the high voltageprimary of the transformer 88 is electrically connected to the motorleads 31 1 and 38 by means of the shunt wires'95 and 96, as shown, sothat the transformer will be energized whenever the motor switch isclosed and the motor is operating.

The circuit-breaker, which is actuated by the action of the combustionthermostat, will next 7 be described, after which the operation of thesafety means will be described in connection with the thermostaticallycontrolled relay circuit controlling the operation of the burner motorand therefore the fuel feeding means. The circuitbreaker, showndiagrammatically in Figure 6, comprises aconductor strip 91 secured to aterminal post 98 to which is connected one end of the portion of thewire I6 leading from the contact I4 of the room thermostat. A movableswitch arm 99 is secured to a resilient member IOI mounted upon asupporting strip I02- by means of a terminal post I03. The terminal post98 and I03 obviously are insulated from the supporting strip I02. Oneend of the portion of the wire I6 leading from the transformer 42 isconnected to the terminal post I03. These two posts 98 and I03 aretherefore electrically connected in series with the wire I6 which leadsfrom the post I4 of the room thermostat to the transformer 42 so thatthe normal engagement of the switch arm 99 with the conductor strip 91of the circuit breaker does not interrupt the thermostaticallycontrolled circuit at the wire I6.

The means provided for automatically moving the switch arm 99 out ofcontact with the-conductor strip 91 to break the circuit, in caseofignition failure, preferably consists of a thermobar I04 having one endsecured to a support I05 secured to the supporting strip I02. The outeror free end of the thermo-bar has a reduced portion forming a tab I05which is adaptednonnally to be received within an angular recessprovided in the depending off-set end I01 of the movable switch arm 99of the circuit breaker. A heating coil I08 is coiled about, thethermo-bar and has one end connected by a wire I09 to the wire 81-leading to one side of the secondary of the transformer88. The other endof the heating coilis similarly connected by a wire III to the wire 4|leading from the intermediate contact post II of the combustionthermostat to the post 34 of the motor switch. The circuit-breaker is soconstructed and arranged that, upon the passage of current through theheating coil I90 for'a predetermined interval, the thermo-bar I04 willbe warped out of engagement with the off-set end ID! of the movableswitch arm 99, which is mounted so that its inherent resilience willcausethe arm 99 to assume the position shown in dotted lines in Figure 6with the result that the switch arm 99 is moved out of contact withtheconductor strip 91 and the thermostatic circuit is broken across thewire I6 and the relay, or electromagnet 23 is de-energized and the motorcircuit is broken at the switch contacts 3|. The apparatus canthereafter only be re-conditioned for normal operation by the manualre-setting of the circuitbreaker switch arm 99, such, for example, as bya push button'IIZ, preferably mounted in the supporting strip I02 of thecircuit-breaker.

In the operation of this novel safety means in connection with thethermostaticallycontrolled relay circuit of the burner motor and fuelfeeding means, the apparatus, after a predeterminedroom temperature isreached, will be in the position shown in Figure 6, wherein it will benoted that the contact blades I2 and I i of the room thermostat are outof electrical contact with the contacts I3 and i4. When thus positionedthe circuit through wire I of the relay will be broken at theroom-thermostat thereby causing the electromagnet 23 to becomede-energized, which will cause the motor switch to be automaticallyopened 25 of the armature 24. Such opening of the motor switch will alsocause the switch arm 45 to be moved out of electrical contact with thecontact 46. When the room thermostat and motor 'trical connection withone another, as shown in Figures 1 and 6.

When the contacts of the combustion thermostat are thus closed, the wireM of the relay circuit will be electrically-connected to the wire I5leading to the room thermostat so that current may flow from theelectromagnet 23 through the wire 4|, combustion thennostat, wire I5 tothe contact screw I3 of the room thermostat where it will be interrupteduntil the tip I 8 of the blade I2 is moved into contact with the contactscrew I3. It will also be noted that when the contacts of the combustionthermostat are in closed posi tion, that the heating coil I08 and alsothe ignition means will be connected in series with the secondary of thetransformer 88 so that when the burner motor resumes operation by theautomatic closing of the motor switch by the action of the roomthermostat that ignition will also be simultaneously resumed.

As soon as the room temperature begins to lower the contacts I8 of theblades I2 and I! of the room thermostat will move towards the contactscrews I3 and I4 until the tip I8 of the blade I1 is moved intoelectrical connection with the contact I4. no effect on the apparatus asa result of the blade I2 being out of contact with the contact I3, andalso as a result of the separated relation of contaft 46 and the blade45. Further cooling of the room will cause the tip I8 of the blade I2 tobe moved into electrical connection with the con tact screw I3 therebycompleting or closing the relay circuit which will be as follows: Fromthe.

secondary of the transformer 42 through the wire I6 and circuit breakerinterposed therein, contact screw I4, blades I! and I2, contact screwI3, wire I5, to the terminal post 69 of the combustion thermostat;through the casing of the latter to the contact screw 54, tips 65 of theswitch member 64, post I2, connection 13 to the intermediate terminalpost II; thence through the wire 4| to-= the electromagnet 23 and backto the other side of the transformer secondary. Closing of the abovecircuit will cause the electromagnet 23 to become energized resulting inthe armature 24 being upwardly drawn thereby resulting in the weight 28dropping and automatically closing the switch arms 29. Such closing ofthe motor switch will cause the motor I and the ignition means to resumeoperation with the resultant operation of burner under normalconditions. As soon as combustion has thus been started, the heat ofcombustion will affect the thermo-element 49 causing it to elongate andthereby actuating the switch mechanism mounted in the combustionthermostat. The first movement of the thermo-element 49, upon com- Suchconnection, however, will have V bustion resumption, will cause one ofthe tips 65 of the blade 66 to be moved out of electrical c0nta:t withthe contact screw '14 as shown in Figure 4, thereby breaking the circuitto the wire M at the combustion thermostat, which will interrupt theflow of current through the heating coil I08 and will therefore renderthe circuit-breaker inoperative. Such breaking of the circuit to thewire H at the combustion thermostat will also,.open the previouslydescribed relay circuit including the wire I5. The electromagnet 23,however, will remain energized to attract side of the secondary of thetransformer 42 through the wire I6 and circuit-breaker to the contactscrew I4 of the room thermostat; thence through the blade I1, coiledthermo-bar II, wire 22, contact 46, switch arm 45, wire H to theelectromagnet 23 and thence back to the other side of the transformer.

Referring further to the operation of the combustion thermostat, aftercombustion has been resumed and the heating coil I08 has beendeenergized, as above described, the contact screw 54 of the switch arm53 will be moved out of electrical connection with its complementary tip65 of the flexible switch member 64, as shown in Figure 5, thereby alsointerrupting the ignition means whichpondition will obtain until theroom temperature rises and the electromagnet circuit is broken throughthe room thermostat, after which the entire apparatus will be renderedinoperative and combustion will cease. Upon such interruption ofcombustion the thermo-element 49 of the combustion thermostat will beginto cool, and first condition theignition circuit for re-energizationafter which the heating coil I08 will be conditioned for re-energizationand 'the combustion thermostat positioned for the next cycle ofoperation.

An important feature in the operationfof the safety means including thecombustion thermostat and circuit-breaker is that in case of'temporarypower failure and immediate resumptionthereof when the burner isnormally running and the room thermostat is in electrical contact withthe contact screws I3 and I4, it will be impossible for the burner toresume operation until after the thermo-element 49 of the combustionthermostat has cooled suiiiciently to present or close the ignitioncircuit before the electromagnet becomes energized to close the motorswitch. This is accomplished by the timed relation of the open-. ing andclosing of the switch contacts in the stack thermostat which are soarranged that the ignition circuit is always closed before the motor orpower feeding means is started after having been accidentallyinterrupted.

In the event of ignition failure when the fuel feeding means is startedby the closing of the main motor switch by the indirect action of theelectromagnet 23 and the room thermostat, the th ermo-element of thecombustion thermostat will not become heated, thereby causing thecontacts 54, 65 and 14 thereof to remain in circuit-closing position sothat current will flow through the heating coil I08 which will cause thethermobar I04 to warp and be moved out of contact with the off-set endportion I01, thereby causing the time required to open thecircuit-breaker by the flow of current through the heating coil I08 isgreater than that required by the thermo-element 49 of the combustionthermostat to open the circuit-breaker circuit to render it inoperative,

so that upon normal operation of the burner the circuit-breaker willalways remain in closed position. The initial starting operation of theburner ignition under normal conditions will be started simultaneouslywith the starting of the 10 motor or fuel-feeding means, and at the sametime current will. be caused to flow through the heating coil I08 of thecircuit breaker which circuit, however, will soon thereafter be openedthrough the combustion thermostat after combustion is started, afterwhich ignition will subsequently be interrupted and the burner willcontinue to function until interrupted by the action of the roomthermostat.

In- Figure '7 there is shown slightly modified 80 construction whereinthe ignition means is connected in series with the secondary of thetransformer 88 and is not controlled by the-operation of the combustionthermostat,.which in the construction here shown is provided with twocon tacts only instead of three as shown in the previous figures. In thearrangement of the parts as here shown, the ignition, under ordinaryconditions, will function each time the burner motor 'I is started andwill continue to function as long as the motor is operating, it beinginterrupted only when the motor or fuel feeding means is interrupted.

In the construction here shown, the heating coil I08 is similarlyconnected in series with the sec- 85- ondary of the transformer 88. A-wire I09 connects one end of the coil to the wire 89 of the transformer,and a wire III connects the other end thereof to the movable switch armII3 of the combustion thermostat having the contact 40 screw II4adjustably mounted therein adapted to engage a stationary contact II5mounted upon the disc 62, which disc is mounted in a manner similar tothat shown and described with reference to the previous figures. A wireIIG leads from the stationary contact II5 to the wire 81 leading to theother side of the secondary of the transformer 80. In the wiringdiagram, Figure 7, the parts are shown in the position assumed when thedesired room temperature has been reached 0 and the blades of the roomthermostat have been moved out of electrical contact with the contactscrews I3 and I4. When the blades of the room thermostat are moved intoelectrical contact with the screws I 3 and I 4, a circuit will becompleted through the electromagnet which will be as follows:

From one side of the secondary of the transformer 42, through the wireI8 and the circuitbreaker to the contact screw I4, through the blades I2and H of the room thermostat to the contact screw l3, wire I5, throughthe movable switch arm II3 of the 'combustion thermostat; thence throughthe contacts H4 and H5 to the wire 4|; to the electromagnet 28 andthence back to the other side of the secondary of the transformer. Theclosing of the above circuit will by flow through the heating coll I08,tending to warp the thermo-bar I 04 to cause thecircuit breaker to openthe wire it upon closure of motor switch 29. Should combustion takeplace, however, then the contact screw IM mounted in the movable switcharm H3 will be moved out of electrical connection with the stationarycontact H5 as a result of the heating of the thermoelement 49, therebyopening the heating coil circult and rendering the circuit-breakerinoperative which condition will obtain as long as the burner continuesto normally function.

The above parts are also so arranged that in case of temporary powerfailure, the relay circuit will be opened and the burner or fuel-feedingmeans cannot possibly again be started before the thermo-element of thecombustion thermostat has cooled sufficiently to allow the contact screwH4 thereof to be moved into engagement with the contact H5, therebyclosing the relay circuit with the resultant starting of the burnermotor and therefore the ignition.

I claim as my invention:

v 1. In' a burner control system, fuel feeding means, a thermostaticallycontrolled circuit which renders the fuel feeding means operative tofeed fuel when completed, a circuit to maintain operation of said fuelfeeding means, said circuit being rendered operative as a result ofcompletion of said thermostatically controlled circuit, a safety meansincluding a circuit-breaker in said first mentioned control circuitoperable automatically upon closure of the circuit to break the circuitafter a predetermined interval, and a device re.-

sponsive to combustion conditions operative upon the establishment ofcombustion to render said circuit-breaker and starting circuitinoperativev 2. In a burner control system, fuel feeding means, athermostatically controlled circuit which renders the fuel feeding meansoperative to feed fuel when completed, a safety means including acircuit-breaker in said control circuit normally operable automaticallyto break the circuit after a predetermined interval, electricallycontrolled ignition means'and a device responsive to combustionconditions and electrically connected in said control circuit and tosaid ignition means effective upon completion of said thermostaticallycontrolled circuit to render inoperative both the circuit-breaker andignition means upon the establishment of combustion.

3. The combination of an electrically operable fuel feeding apparatusand a circuit therefor with a switch in the circuit, a relay to controltheswitoh, a thermostatic means and starting circuit therefor toenergize the relay, a holding circuit operative after relay closure, acut-out mechamechanism automatically operable after a time period tointerrupt the relay circuit upon closure of said relay switch, ignitionmeans electrically operable upon closure of said switch and a deviceresponsive to the presence or absence of combustion automaticallyoperable upon the establishment of combustion to render first thecut-out mechanism inoperable and then render the ignition meansinoperable.

5. A combustion apparatus including a burner motor and a power circuitfor the motor including an electrically operable switch, an electricallyoperable timing switch and a control circuit therefor operative to openthe time switch when completed for a time period, starting and holdingcircuits for the motor switch controllable by the timing switch, aswitch'responsive to the establishment of combustion at the burner andhaving contacts controlling the starting and timing switch controlcircuits, said contacts being normally closed in absence of combustion,the circuit arrangement thereby being such that when said contacts areso closed the resulting energization of the timing switch circuit willopen themotor switch control circuit at the end of a predetermined time,if combustion is not established.

6. An electrical system forliquid fuel burners comprising a burnermotor, a circuit for the motor, a mainswitch for controlling thecircuitwhich switch opens automatically. when released,

electrically operated means for closing the main switch and holding itclosed, a second circuit ineluding said switch closing means, and anormally closed safety switch, and a safety circuit including a timingdevice for opening said safety switch, and a switch responsivetooombustio-n conditions, said last mentioned switch being closed in theabsence of and open in the presence of combustion.

7. In a combustion system, the combination of a combustion chamber,means for feeding fuel thereto including an electric motor, means forigniting said fuel, an electric circuit for said motor including aswitch, means for maintaining said switch closed including an electriccircuit having a normally closed safety switch therein, and means foropening said safety ,means for closing the main switch and holdin itclosed, a secondary circuit including sai switch-closing means and anormally-closed safety switch, and a safety circuit including a timeddevice for opening said safety switch and a switch responsive tocombustion conditions,

said last mentioned switch being closed in the absence of and open inthe presence of combustion.

9. An electrical control system for liquid fuel burners comprising aburner motor, a main circuit in which said burner is connected, a switchfor controlling the main circuit, a solenoid for operating said switch,the latter being maintained closed when the solenoid is energized andopening automatically when it is de-energized, a secondary circuitincluding said solenoid, a, source of current, and a normally closedsafety switch, timed means for automatically opening said safety switchat the end of a predetermined interval after the energizing of saidsolenoid, said means being ineffective to close the switch,

. the absence of and open in the presence of combustion in thecombustion chamber, for opening said safety switch automatically andthereby cutting off the fuel to the combustion chamber upon initialfailure of combustion within a predetermined time after said main switchhas been closed.

11. In a combustion system comprising a combustion chamber, means forsupplying fuel to said chamber, and means for igniting said fuel, anelectrical control system including a main electric circuit, a mainswitch in said circuit, a secondary circuit controlling the closing ofsaid main switch, a normally closed safety switch in said secondarycircuit, and means for automatically opening said safety switch uponinitial failure of combustion within a predetermined time after saidmain switch has been closed,

:thereby causing the opening of the main switch,

said means being ineffective to close the safety switch. I

12. An electrical control system for liquid fuel burners comprisingelectrically operated means for projecting fuel into a zone of ignition,means for igniting said fuel, a main electric circuit including, said,fuel projecting means, a main switch in said circuit, means forautomatically opening said main switch including a normallyclosed safetyswitch, means for automatically opening said safety switch, therebycausing the opening of the main switch including an electric circuit anda heating coil therein, said means being timed to open said safetyswitch at the end of a predetermine interval after the closing of themain switch, and said circuit including the heating coll being closedupon theclosing of the main switch, and means for breaking said circuitincluding the heat coil upon the initiation of combustion.

13. An electrical control system for liquid fuel burners comprisingelectrically operated means for projecting fuel into a. zone ofignition, means for igniting said fuel, a main electric circuitincluding said fuel projecting means, and

safety means for automatically breaking said main circuit upon thefailure of combustion, said safety means including a secondary circuitand means, including a. circuit closer responsive to combustionconditions and closed in the absence of and open in the presence ofcombustion in the combustion chamber, for automatically breaking saidsecondary circuit and thereby breaking the main circuit at the end of apredetermined interval after the closing of the main circuit, in thetion conditions, controlling said second circuit, which switch is closedin the absence of and open in the presence of combustion in thecombustion chamber, said last named switch also controllingthe normalstarting of the fuel supply means.

15. In a combustion system comprising a combustion chamber, means forsupplying fuel thereto, and means for igniting said fuel, anelectricalcontrol system comprising a main circuit includ- 10 ing said fuelprojecting means, safety means for automatically breaking said maincircuit upon the failure of combustion, said safety means including asecond circuit and a normally closed safety switch therein, means forautomatically opening said safety switch, and a switch responsive tocombustion conditions, closed in the absence of and open in the presenceof combustion in the combustion chamber, said last named switchcontrolling the automatic opening of the 20. safety switch and theclosing of the main circuit in normal starting of the fuel supply means.

16. In a combustion system comprising a combustion chamber, means forsupplying fuel to said chamber and means for igniting said fuel, anelectrical control system, including a main circuit, a main switch insaid circuit, a second 01rcuit controlling the closing of the mainswitch, a normally closed safety switch in said second circuit and meansfor opening said safety switch automatically, a switch responsive tocombustion conditions controlling said second ,circuit,

which switch is closed in the absence of and open in the presence ofcombustion in the combustion chamber, a second switch in the secondcircuit which is automatically closed at the time the main switchoperates toclose, said second switch'being for the purpose ofestablishing a parallel circuit to the switch which is responsive tocombustion conditions, said switch which is 4o and including meanscontrolled by the tempera, i

ture of combustion-interposing a. delay between successive motorenergizations when said main switch is closed.

18. In a burner control system, a main switch, a burner motor, ignitionmeans, means to place said burner motor and ignition means in operationin response to closure of said main switch and to stop operation of theburner motor in response to opening thereof, and including meanscontrolled by the temperature of combustion interposing a delay betweensuccessive motor energizations and terminating operation of the 0,ignition means upon the establishment of com-'. bustion while said mainswitch is closed.

19. In a burner control system, a main switch, a burner motor, means tostart the burner motor in response to closure of said main switch and tostop the same in response to opening thereof, and including meanscontrolled by the temperature of combustion for preventingre-energization of said burner motor until the temperature of combustionhas lowered at least a predeterf mined amount after cessation ofcombustion resulting from a temporary failure in electrical power.

20. In a burner control system, a main switch,

a burner motor, means to start said burnermotor in response to closureof said main switch and to stop the same in response to opening thereof,a thermal-electric safety timer including an electric heating elementfor terminating operation of said burner motor after'a predeterminedtime and until manual intervention if combustion is not established,said electric heating element being energized by said means in responseto closure of said main switch, and including means controlled by thetemperature of combustion for operatively de-energizing said safetytimer if combustion is established and for interposing a delay betweensuccessive energizations of said burner motor.

21. A system of the class described, comprising, in combination, anelectrically operable fuel supply controlling device, an energizingcircuit therefor, a. switch in control of said circuit, electricallyoperated means (operable to move said switch to closed position whenenergized, said switch moving to open position upon de-energization ofsaid electrically operable means, a main control switch, switching meanscontrolled by the temperature of combustion and including a switch whichis open in the presence of and closed in the absence of combustion, anenergizing circuit for said electrically operable means controlled bysaid switch of the combustion responsive switching means and said maincontrol switch in series, and connections for maintaining energizationof said electrically operable means after the establishment ofcombustion.

22. An oil burner control system comprising, a burner motor, a burnermotor circuit, a motor switch, electromagnetic means for closing saidmotor switch when energized and for opening the same when deenergized, asafety switch mechanism comprising a thermally operated switch and anelectrical heating means therefor, means for maintaining said thermallyoperated switch in open position until manual intervention when the sameis opened' as a result of a predetermined heating by said electricalheating means, a main control switch, eectrical ignition means,combustion responsive switching mechanism closed in the absence of andopen in the presence of'combustion, circuit connections for saidelectromagnetic means, electrical heating means and ignition meanscontrolled by said main control switch and combustion responsiveswitching mechanism, a holding switch moved to closed position uponenergization of said electromagnetic means, and a holding circuit forsaid electromagnetic means independent of said combustion responsiveswitching mechanism and controlled by said main control switch and saidholding switch.

23. A combustion control system including in combination, a roomthermostat having sequentially engageable contacts, a relay coil, 9.motor switch, a holding. switch, said motor switch and holding switchboth being operated by the relay coil to close upon energization of thecoil and automatically open when the coil is de-energized,

a burner motor, a combustion responsive switch having contacts closed inthe absence of and open in the presence of combustion, a circuit for.initially energizing the relay coil including in series the contacts ofthe combustion switch and the last to close contact of said sequentiallyengageable,

room thermostat contacts, and a holding circuit for the relay coilincluding in series the contacts of said holding switch and the first toclose contact of said sequentially engageable room thermostat contacts,said holding circuit being independent of said combustion switchcontacts.

24. A system of the class described for heating a space, comprising, incombination, a heater, an electrically operable fuel supply controllingdevice for heating said heater, an energizing circuit therefor, a switchin control of said circuit, a hold- 5 ing switch, electrically operatedmeans operable to move said switches to closed position when energized,said switches moving to open position upon de-energization of saidelectrically operable means, a space temperature responsive main con- 10trol switch that closes upon a, fall in the space temperature, switchingmeans controlled by a heater condition and including a switch which isopened upon an increase in the value of said heater condition and isclosed upon a fall in the 15 value of said heater condition, anenergizing circuit for said electrically operable means controlled bysaid switch of the heater condition responsive switching means and saidmain control switch in series, and connections including the 20 maincontrol switch and holding switch in series for maintaining energizationof. said electrically operable means after said switch of the heatercondition responsive switching means opens as a result of operation ofsaid fuel supply controlling 25 device.

25. The combination of an electrically operable fuel feeding apparatusand circuit therefor with a switch in the circuit, a relay to controlthe switch, starting and holding circuits for said re- 30 lay includinga thermostatic means, a cut-out mechanism automatically operable after atimed period to interrupt said relay circuits upon closure of said relayswitch, said holding circuit being rendered operative as a result ofcompletion 35 of said starting circuit, and a combustion responsiveswitching device automatically operable upon the establishment ofcombustion to render said cut-out mechanism and starting circuitinoperable and upon subsequent combustion failure, to 4,0 again rendersaid cut-out mechanism operable whereby to stop fuel feeding.

26. The combination of an electrically operable fuel feeding apparatusand a circuit therefor with a switch in the circuit, a relay to controlthe switch, a thermostatic means and circuit therefor to control therelay, a cut-out mechanism automatically operable after a timed periodto interrupt the relay circuit upon closure of said relay-switch,electrically operable ignition means, and a combustion responsive deviceautomatically operable upon the establishment of'combustion to rendersaid cut-out mechanism and-said ignition means inoperable.

27. In a burner control system, in combination, a burner motor, a burnermotor circuit, a burner motor switch operative to complete the burnermotor circuit when closed, a control circuit operative to close saidburner motor switch when completed, a thermostat operative to completesaid controlxcircuit 'upon a call for heat and to interrupt the samewhenthe room thermostat becomes satisfied, said burner motor switchautomatically moving to opened position upon interruption of saidcontrol circuit, and means responsive to combustion conditions operativeto permit closure of the burner motor switch only after the temperatureof combustion has decreased a predetermined amount as the result of apriorcessation of combustion.

able to open position, a control circuitoperative to close the burnermotor switch when completed, a combustion responsive device including aswitch which closes upon a predetermined lowering in the temperature ofcombustion and opens" upon the establishment of combustion, a roomthermostat,

said control circuit including the room thermostat and said switch oithe combustion responsive mechanism, whereby the control circuit canonly be completed by the room thermostat if the temperature ofcombustion has decreased at least said predetermined amount, and meanscontrolled by said room thermostat operative to maintain said burnermotor switch closed after opening of said switch of the combustionresponsive mechanism.,

29. In a burner control system in combination, a'burner motor, a burnermotor circuit, a motor switch in control of said circuit, anelectro-magnet operative to close the motor switch when energized, themotor switch automatically moving to open position upon deenergizationof the electromagnet, a combustion responsive mechanism in- 1 eluding aswitch that closes only after the temperature'of combustion lowers atleast a predetermined amount and which opens upon the establishment ofcombustion, a room thermostat, a circuit for the electro-magnetcontrolled by the room thermostat and said switch of the combustionresponsive mechanism whereby the motor switch can be closed only afterthe temperature of combustion has decreased at least said predeterminedamount, and means including electrical connections controlled by theroom thermostat operative to maintain said motor switch closedafteropening of said switch of the combustion responsive mechanism as aresult oi the establishment of combustion.

30. An electrical control system for liquid fuel burners comprising aburner motor, a motor circuit in which said motor is connected, a motorswitch in said motor circuit which opens automatically when released,electrically operated means operative to close the motor switch and tohold it closed when energized, a control circuit including saidelectrically operated means, a safety switch including a timeddevice'operative to render the system inoperative if energized for atimed period, and a combustion responsive switch in control of theenergization of said timed device, said last-mentioned switch beingclosed in the absence of and open in the presence of combustion.

31.An electrical control system for liquid fuel burners comprising aburner motor, a motor circuit in which said motor is connected, a motorswitch in said motor circuit which opens automatically when released,electrically operated means operative to close the motor switch and tohold it closed when energized, a control circuit including saidelectrically operated means, a safety switch including a timed deviceoperative to render the system inoperative if energized for a timedperiod, a combustion responsive switch a in control of the energizationof said timed device, said last-mentioned switch being closed in theabsence of and open in the presence of combustion, and also controllingthe initial energize.- tion of said electrically operated means, andmeans to maintain said motor switch closed after opening of saidcombustion responsive upon the establishment of combustion.

32. A system of the class described, comprising, in combination, anelectrically operable fuel supply controlling device, a main controlswitch, a combustion responsive switching mechanism ineluding a switchwhich is open in the presence of and closed in the absence ofcombustion, a thermal safety switch including an electrical heatingelement operative to render the system inoperative if energized for apredetermined 5 length of time, and means including circuit conectionscontrolled by said switch of the combus tion responsive switchingmechanism and said main control switch in series operative to initiallyenergize said fuel supply controlling device and 10 heating element, andincluding circuit connections completed through said main control switchoperative to maintain energization only of said fuel supply controllingdevice after combustion is established. 16 33. A system of the classdescribed, comprising,

in combination, an electrically operable fuel supply controlling device,a manually resettable thermal time switch including a thermal element tomechanically actuate said time switch to open 20 position when heated toa predetermined degree and an electrical heating element to heat saidthermal element, a combustion responsive switch operable to open circuitposition upon the -es tablishment of combustion, a main control switch,25 and means including circuit connections completed through said maincontrol switch, time switch and combustion responsive switch forenergizing said fuel supply controlling device and heating element upona call for heat during the absence of combustion and for maintainingenergization only of said fuel supply control device after combustion isestablished.

' 34. A burner control system comprising, in combination,a burner motor,ignition means,elec- 35 trically operated safety means operative torender the system inoperative after a time period and including meanswhich must be deenergized be- .fore said period elapses if the system isto continue in operation, combustion responsive switch- 40 ing mechanismincluding first and second switches which open in the order named uponthe establishment of combustion and close upon the cessation ofcombustion, a main control, circuit connections including the foregoingelements and 5 controlled by the main, control and first switchoperative to energize the burner motor and igni tion means and toenergize said means of the safety means upon a call for heat, and tomaintain energization of the ignition means until 50 opening of saidsecond switch,. and means to maintain energization of the burner motorafter opening of said first and second switches.

35. A burner control system comprising, in combination, a burner motor,electrically 'oper- 55 ated ignition means, a motor switch, electricallyenergizable means operative to close the motor switch when energized,the motor switch automatically moving to open position when theelectrically energizable means is deenergized, combustion responsiveswitching means which opens upon the establishment of combustion andwhich closes only after the temperature of combustion has decreased atleast a predetermined amount, 65

' a main control switch, an initial energizing circuit for theelectrically energizable means controlled by the main controlled switchand combustion responsive switching means in series, circuit connectionsoperative to maintain energiza- 7 tion of said electrically energizablemeans after opening of the combustion responsive switching meanscontrolled by said main control switch, a burner motor circuitcontrolled by the motor switch, and an ignition means circuit controlledtor in response to closure of said main switch and to stop the same inresponse to opening thereof, a thermal-electric safety timer includingan electric heating element for terminating operation of said burnermotor after a predetermined time and until manual intervention ifcombustion is not established, said electric heating element beingenergized by said means in response to closure of said main switch, andincluding means controlled by the temperature of combustion foroperatively de-energizing said safety timer if combustion is establishedand for interposing a delay between successive energizations of saidburner motor.

21. A system of the class described, comprising, in combination, anelectrically operable fuel supply controlling device, an energizingcircuit therefor, a switch in control of said circuit, electricallyoperated means (operable to move said switch to closed position whenenergized, said switch moving to open position upon de-energization ofsaid electrically operable means, a main control switch, switching meanscontrolled by the temperature of combustion and including a switch whichis open in the presence of and closed in the absence of combustion, anenergizing circuit for said electrically operable means controlled bysaid switch of the combustion responsive switching means and said maincontrol switch in series, and connections for maintaining energizationof said electrically operable means after the establishment ofcombustion.

22. An oil burner control system comprising, a burner motor, aburnermotor circuit, a motor switch, electromagnetic means for closing.said motor switch when energized and for opening the same whendeenergized, a safety switch mechanism comprising a thermally operatedswitch and an electrical heating means therefor, means for maintainingsaid thermally operated switch in open position until manualintervention when the same is opened as a result of a predeterminedheating by said electrical heating means, a main control switch,eectrical ignition means, combustion responsive switching mechanismclosed in the absence of and open in the presence of combustion, circuitconnections for said electromagnetic means, electrical heating means andignition means controlled by said main control switch and combustionresponsive switching mechanism, a holding switch moved to closedposition upon energization of said electromagnetic means, and a holdingcircuit for said electromagnetic means independent of said combustionresponsive switching mechanism and controlledby said main control switchand said holding switch.

23. .A combustion control system including'in combination, a roomthermostat having sequenti- .ally engageable contacts, -a relay coil,amotor switch, a holding switch, said motor switch and holding switchboth being operated by the relay coil to close upon energization of thecoil and automatically open when the coil is de-energized,

a burner motor, a combustion responsive switch having contacts closed inthe absence of and open in the presence of combustion, a circuit for.initially energizing the relay coil including in series the contacts ofthe combustion switch and the last to close contact of said sequentiallyengageable.

room thermostat contacts, and a holding circuit for the relay coilincluding in series the contacts of said holding switch and the first toclose contact of said sequentially engageable room thermostat contacts,said holding circuit being independent of said combustion switchcontacts.

24. A system of the class described for heating I a space, comprising,in combination, a heater, an

electrically operable fuel supply controlling device for heating saidheater, an energizing circuit therefor, a switch in control of saidcircuit, a holding switch, electrically operated means operable to movesaid switches to closed position when energized, said switches moving toopen position upon de-energization of said electrically operable means,a space temperature responsive main control switch that closes upon afall in the space temperature, switching means controlled by a heatercondition and including a switch which is opened upon an increase in thevalue of said heater condition and is closed upon a fall in the value ofsaid heater condition, an energizing circuit for said electricallyoperable means eontrelled by said switch of the heater conditionresponsive switching means and said main control switch in series, andconnections including the main control switch and holding switch inseries for maintaining energization of. said electrically operable meansafter said switch of the heater condition responsive switching meansopens as a result of operation of said fuel supply controlling device.

25. The combination of an electrically operable fuel feeding apparatusand circuit therefor with a switch in the circuit, a relay to controlthe switch, starting and holding circuits for said relay including athermostatic means, a cut-out mechanism automatically operable after atimed period to interrupt said relay circuits upon closure of said relayswitch, said holding circuit being rendered operative as a result ofcompletion of said starting circuit, and a combustion responsiveswitching device automatically operable upon the establishment ofcombustion to render said cut-out mechanism and starting circuitinoperable and upon subsequent combustion failure, to 40 again rendersaid cut-out mechanism operable whereby to stop fuel feeding.

26. The combination of an electrically operable fuel feeding apparatusand a circuit therefor with a switch in the circuit, a relay to controlthe switch, a thermostatic means and circuit therefor to control therelay, a cut-out mechanism automatically operable after a timed periodto interrupt the relay circuit upon closure of said relay-switch,electrically operable ignition means, and a combustion responsive deviceautomatically operable upon the establishment of'combustion to rendersaid cut-out mechanism and said ignition means inoperable.

27'. In a burner control system, in combination, a burner motor, aburner motor circuit, a burner motor switch operative to complete theburner motor circuit when closed, a control circuit operative to closesaid burner motor switch when completed, a room thermostat operative tocomplete said controltlcircuit upon a call for heat and to interrupt thesame when the room thermostat becomes satisfied, said burner motorswitch automatically moving toopened position upon interruption ofsaid.- control circuit, and means responsive to combustion conditionsoperativeto permit closure of the burner motor switch. only after thetemperature of combustion has decreased a predetermined amount as theresult of a prior cessation of combustion.

able to open position, a control circuitoperative 76 to close the burnermotor switch when completed, a combustion responsive device including aswitch which closes upon a predetermined lowering in the temperature ofcombustion and opens'upon the establishment of combustion, a roomthermostat, said control circuit including the room thermostat and saidswitch of. the combustion responsive mechanism, whereby the controlcircuit can only be completed by the room thermostat if the temperatureof combustion has decreased at least said predetermined amount, andmeans controlled by said room thermostat operative to maintain saidburner motor switch closed after opening of said switch of thecombustion responsive mechanism.

29. In a burner control system in combination, a burner motor, a burnermotor circuit, a motor switch in control of said circuit, anelectro-magnet operative to close the motor switch when energized, themotor switch automatically moving to open position upon deenergizationof the electromagnet, a combustion responsive mechanism including aswitch that closes only after the temperature'of combustion lowers atleast a predetermined amount and which opens upon the establishment ofcombustion, a. room thermostat, a circuit for the electro-magnetcontrolled by the room thermostat and said switch of the combustionresponsive mechanism whereby the motor switch can be closed only afterthe temperature of combustion has decreased at least said predeterminedamount, and means including electrical connections controlled by theroom thermostat operative to maintain said motor switch closed afteropening of said switch of the combustion responsive mechanism as aresult of the establishment of combustion.

30. An electrical control system for liquid fuel burners comprising aburner motor, a motor circuit in which said motor is connected, a motorswitch in said motor circuit which opens automatically when released,electrically operated means operative to close the motor switch and tohold it closed when energized, a control circuit including saidelectrically operated means, a safety switch including a timeddevice'operative to render the system inoperative if energized for atimed period, and a combustion responsive switch in control of theenergization of said timed device, said last-mentioned switch beingclosed in the absence of and open in the presence of combustion. I

31. An electrical control system for liquid fuel burners comprising aburner motor, a motor circuit in which said motor isconnected, a. motorswitch in said motor circuit which opens automatically when released,electrically operated means operative to close the motor switch and tohold it closed when energized, a control circuit including saidelectrically operated means, a safety switch including a timed deviceoperative to render the system inoperative if energized for a timedperiod, a combustion responsive switch in control of the energization ofsaid timed device, said last-mentioned switch being closed in theabsence of and open in the presence of combustion, and also controllingthe initial energization of said electrically operated means, and meansto maintain said motor switch closed after opening of said combustionresponsive upon the establishment of combustion.

32. A system of the class described, comprising, in combination, anelectrically operable fuel supply controlling device, a main controlswitch, a combustion responsive switching mechanism intem inoperative ifenergized for a predetermined 5 length of time, and means includingcircuit conections controlled by said switch of the combustionresponsive switching mechanism and said main control switch in seriesoperative to initially energize said fuel supply controlling device and10 heating element, and including circuit connections completed throughsaid main control switch operative to maintain energization only of saidfuel supply controlling device after combustion is established. 15

33. A system of the class described, comprising, in combination, anelectrically operable fuel supply controlling device, a manuallyresettable thermal time switch including a thermal element tomechanically actuate said time switch to open 20 position when heated toa predetermined degree and an electrical heating element to heat saidthermal element, a combustion responsive switch operable to open circuitposition upon the establishment of combustion, a main control switch, 25and means including circuit connections completed through said maincontrol switch, time switch and combustion responsive switch forenergizing said fuel supply controlling device and heating element upona call for heat during the absence of combustion and for maintainingenergization only of said fuel supply control device after combustion isestablished.

34. A burner control system comprising, in combination,a burnermotor,igniti0n means,electrically operated safety means operative torender the system inoperative after a time period and including meanswhich must be deenergized benections including the foregoing elementsand 5 controlled by the main. control and first switch operative toenergize the burner motor and ignition means and to energize said meansof the safety means upon a call for heat, and to maintain energizationof the ignition means until 50 .opening of said second switch, and meansto maintain energization of the burner motor after opening of said firstand second switches.

35. A burner control system comprising, in combination, a burner motor,electrically oper- 55 ated ignition means, a motor switch, electricallyenergizable means operative to close the motor switch when energized,the motor switch automatically moving to open position when theelectrically energizable means is deenergized, combustion responsiveswitching means which opens upon the establishment of combustion andwhich closes only after the temperature of combustion has decreased atleast a predetermined amount, 65

a main control switch, an initial energizing circuit for theelectrically energizable means controlled by the main controlled switchand combustion responsive switching means in series, circuit connectionsoperative to maintain energiza- 7 tion of said electrically energizablemeans after by the conjoint action of the motor switch and combustionresponsive switching means.

36. A systern'of the class described, comprising, in combination, anelectrically operable fuel supply cc-ntrolling device, electricallyoperable ignition means for igniting the fuel supplied by said device,first and second switches, a fuel supply controlling device energizingcircuit controlled by said first switch, an ignition means energizingcircuit controlled by said second switch, an element responsi've'tocombustion conditions operative to close said second and first switchesseand to maintain energization of said fuel supply controlling deviceafter opening of said first switch upon the establishment of combustion.

37. A system of the class described, comprising, in combination, anelectrically operable fuel supply controlling device, ignition meansoperative to ignite the fuel supplied by said fuel supply controllingdevice, switching means responsive to combustion conditions and includng first and second. switches which are closed in the order named uponcessation of combustion, a main control switch, said first switch beingin circuit with said iginition means, means including circuitconnections controlled by said main control switch and second switch inseries operative to initially energize said fuel supply controllingdevice and ignition means whereby said ignition means is conditioned foroperation by closure of said first switch before the entire system isconditioned. for operation by closure of said second switch, and meansoperative to maintain energization of said fuel supply controllingdevice after combustion is established.

38. A system of the class described, comprising, in combination, anelectrically operable fuel sup-ply controlling device, an energ'zingcircu t therefor, a switch in control of said circuit, electricallyoperable means operable to move said switch to closed position whenenergized, a main control switch, switching means controlled by thetemperature of combustion and including first and second switches closedin the order named upon cessation of combustion, electrically operableignition' means, a circuit therefor controlled by the conjoint action ofsaid first-named switch and the first switch of said combustionresponsive switching means, an energizing circuit for said electricallyoperable means controlled by the conjoint action of said second switchof the combustion responsive switching means and said main controlswitch, and means controlled by said main control switch operative tomaintain energization of said electrically operable means after theestablishment of combustion. p

39. A system of the class described, comprisng, in combination, a fuelcontrol device, ignition means, a cut-out mechanism automaticallyoperable to interrupt the supply of fuel if operated for a predeterminedlength of time, a main control, an element responsive to the presence orabsence of combustion, means including circuit connections between saidmain control and element and said fuel control device, cut-out mechanismand ignition means operative to place said fuel control device, cut-outmechanism, and ignition means into operation upon a call for heat bysaid main control in the absence of combustion and to first render saidcut-out mechanism inoperative and then said ignition means inoperativewhile maintaining the supply of fuel upon the establishment ofcombustion.

40. A system of the class described, comprising, in combination, anelectrically operable fuel supply controlling device, ignition means, asafety mechanism comprising a thermal switch adapted to open when heatedto a predetermined degree and an electrical heating element therefor,combustion responsive switching mechanism including first and secondswitches which open sequentially in the order named upon establishmentof combustion, the second switch closing prior to closing of the firstswitch upon cessation of combustion, a main control switch, and meansincluding circuit connections for energizing said fuel supplycontrolling device, electrical heating element and ignition means uponclosure of said main control switch'only if said first switch is closed,for maintaining energization of said fuel supply controlling deviceafter combustion is established' and for respectively interrupting thecircuits for said heating element and ignition means upon the sequentialopening of said first and second switches.

41. A burner control system of the class described, comprising, incombination, a burner motor, electricaly operated ignition means, arelay including an electromagnetic coil, and a motor switch and acontrol switch that are closed and held closed by said electromagneticcoil when energzed, a burner motor circuit controlled by said motorswitch, first and second switches responsive to combustion conditionswhich close in the order named upon the cessation of combustion and openupon the establishment of combustion, an ignition means circuitcontrolled by the conjoint action of the motor switch and said firstswitch, a maincontrol switch, an initial energizing circuit for theelectromagnetic coil controlled by the train control switch and saidsecond switch in series, and a hold'ng circuit for the electromagneticcoil which is independent of said second switch but includes the maincontrol switch and holding switch in series.

42. A burner control system of the class described, ccmprising, incombination, a burner motor, electrically operated ignition means, a

- motor switch and a control switch that are closed and held closed bysaid electromagnetic coil when energized, a burner motor circuitcontrolled by said motor switch, first and second switches responsive tocombustion conditions which close in the order named upon the cessationof combustion and open upon the establishment of combustion, an ignitionmeans circuit controlled by the conjoint action of the motor switch andsaid first switch, a main control switch, a thermoeelectric safetyswitch including an electric heating element and-operative to shut downthe system if its heating element is operatively energized for a timedperiod, energizing circuits for said electromagnetic coil and heatingelement completed only by closure of both the main control switch andsaid second switch, and a holding circuit for the electromagnetic coilcontrolled by the main control switch and holding switch but independentof said second switch.

43. In a burner control system; in combination; a high voltage burnermotor; ignition means; a step-down transformerya motor switch; anenergizing circuit for the burner motor and said transformer controlledb'ysaid motor switch; an electromagnetic coil operable to close saidmotor switch and maintain the same closed when position after opening ofsaid second switch as a energized; a low voltage main control switch:low voltage switching means responsive to combus tion conditions closedin the absence of and open in the presence of combustion; a low voltagecircuit for theelectromagnetic coil controlled by the main controlswitch and said switching means; a circuit including said ignitionmeans, the second ary of said transformer and said switching means; andmeans under the control of said main control switch operative tomaintain energization of said electromagnetic coil after the opening ofsaid switching means by reason of the establishment of combustion;

44. In a burner control system, a motor controlling fuel feed, a roomthermostat circuit, means rendered operative to start said motor inresponse to the closure of said circuit and to stop said motor upon theopening thereof, and combustion responsive means controlling said firstmentioned means and operative when combustion terminates to delay for atime interval reenergization of said motor when said circuit is closed.

45. A system of the class described, comprising, in combination, anelectrically operable fuel supply controlling device, ignition meansoperative to ignite the fuel supplied by said fuel supply controllingdevice, first and second switches controlled by combustion conditions,upon cessation of combustion said first switch moving to a. new controlposition and said second switch thereafter closing, a main controlswitch, means including circuit connections controlled by the mainswitch and second switch in series operative to initially energize saidfuel supply controlling device and ignition means, means operative tomaintain energization' of said fuel supply controlling device andignition means after opening' of said second switch, and meanscontrolled by said first switch to deenergize said ignition means whenthe first switch is moved to a new control result of the establishmentof combustion.

46. A system of the class'described, comprising,

bustion temperature responsive switching means including a first switchthat closes upon a lowering of the combustion temperature apredetermined amount and opens upon a rise in combustion temperature anda second switch moved to a new controlling position upon a rise incombustion temperature greater than that required to open said firstswitch, a main control switch, and circuit connections including theforegoing elements and means for energizing said fuel supply controllingdevice, electrical heating element and ignition means upon closure ofsaid main control switch only if said first switch is closed, formaintaining energization of said fuel supply controlling device aftercombustion is established and for respectively and sequentiallyinterrupting' the circuits for said heating element and ignition meansupon opening of said first switch and movement of said second switch toits new controlling position whereby said heating element is deenergizedprior to said ignition means if combustion is established.

47. A burner control system of the class described, comprising incombination, a burner -motor, electrical ignition means, a burner motorswitch, energizing circuits for said burner motor and ignition meanscontrolled by closure of said burner motor switch, a holding'switch,electromagnetic means to close said burner motor and holding switches, amain control switch, a first combustion responsive switch that closesupon cessation of combustion and opens upon the establishment ofcombustion, a circuit for energizing said electromagnetic means to causeclosure of said burner motor and holding switches and controlled by saidmain switch and first combustion responsive switches in series, acircuit for energizing said electromagnetic means to maintain saidburner motor and holding switches closed after opening of said firstcombustion responsive switch upon the establishment of combustioncontrolled by said main control switch and holding switch in series, anda second combustion responsive switchwhich moves to a new controlposition after opening of said first combustion responsive switchoperative to interrupt said ignition means circuit.

FREDERICK S. DENISON.

